Air-operated reciprocating pumps are in general well known and have been used for many years with a variety of materials. In such pumps typically, a piston reciprocates within a cylinder to pump the fluid which is loaded into the cylinder through a check valve located in the piston. When it has been desired to utilize such types of pumps for highly viscous materials, a so called shovel pump arrangement has been used wherein the piston at the bottom end of its stroke extends beyond the open bottom end of the cylinder to allow material to be taken into the cylinder. While such pumps are each effective with respect to the types of materials for which they are designed, heretofore such pumps have not been easily adapted between types of materials without replacing the whole pump lower assembly. It is, therefore, an object of this invention to provide a pump which may be easily and quickly adapted to pump a variety of materials having widely varying viscosities.